Comprehensive model for VPLS

ABSTRACT

A VPLS model is implemented in a network-facing provider edge (n-PE) device configured to receive a packet from an access network; the packet having a first Virtual Local Area Network (VLAN) tag of a first predetermined bit length. The n-PE device mapping the service instance identifier of the first VLAN tag into a second VLAN tag of a second predetermined bit length greater than the first predetermined bit length, the second VLAN tag identifying a Virtual Private LAN Service (VPLS) instance. The n-PE device then sends the packet with the second VLAN tag across a service provider (SP) core network via a pseudowire (PW) that functions as a logical link to another PE device. It is emphasized that this abstract is provided to comply with the rules requiring an abstract that will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. 37 CFR 1.72(b).

RELATED APPLICATIONS

The present application is related to application Ser. Nos. 11/117,016filed Apr. 28, 2005, entitled, “Metro Ethernet Network With ScaledBroadcast And Service Instance Domains”; 11/117,017 filed Apr. 28, 2005,entitled, “System And Method For DSL Subscriber Identification OverEthernet Network”; and 11/117,249 filed Apr. 28, 2005, entitled,“Scalable System And Method For DSL Subscriber Traffic Over An EthernetNetwork”, which applications are assigned to the assignee of the presentapplication.

FIELD OF THE INVENTION

The present invention relates generally to digital computer networktechnology; more particularly, to methods and apparatus for providingLocal Area Network (LAN) emulation services over Internet protocol (IP)networks.

BACKGROUND OF THE INVENTION

A LAN is a high-speed network (typically 10 to 1000 Mbps) that supportsmany computers connected over a limited distance (e.g., under a fewhundred meters). Typically, a LAN spans a single building. U.S. Pat. No.6,757,286 provides a general description of a LAN segment. A VirtualLocal Area Network (VLAN) is mechanism by which a group of devices onone or more LANs that are configured using management software so thatthey can communicate as if they were attached to the same LAN, when infact they are located on a number of different LAN segments. BecauseVLANs are based on logical instead of physical connections, they areextremely flexible.

The IEEE 802.1Q specification defines a standard for Virtual LAN and itsassociated Ethernet frame format. Broadcast and multicast frames aretypically constrained by VLAN boundaries such that only devices whoseports are members of the same VLAN see those frames. Since 802.1Q VLANscommonly span many switches across different LAN segments, sharing ofVirtual LANs by a common set of infrastructure switches is achieved byinserting a VLAN tag into the Ethernet frame. For example, according tothe existing standard, a VLAN tag with 12-bit VLAN identifier (VLAN ID)is inserted into an Ethernet frame. This VLAN ID may be used to specifythe broadcast domain and to identify the customer associated with aparticular VLAN. The customer identifier is frequently referred to asthe service instance domain since it identifies the service provided fora particular customer. In a typical service provider (SP) metropolitanarea network (MAN) the broadcast domain constrains the scope of trafficamong network devices such that data packets are not multicast to alldevices connected to the network. A system and method for efficientlydistributing multicast messages within computer networks configured tohave one or more VLAN domains is disclosed in U.S. Pat. No. 6,839,348.

A Virtual Private Network (VPN) enables IP traffic (the Internet isbasically a conglomeration of WANs) to travel securely over a publicTransmission Control Protocol (TCP)/IP network by encrypting all trafficfrom one network to another. A VPN uses “tunneling” to encrypt allinformation at the IP level. In a Layer 3 IP VPN, customer sites areconnected via IP routers (e.g., provider edge (PE) devices and nodes)that can communicate privately over a shared backbone as if they areusing their own private network. Multi-protocol label switching (MPLS)Border Gateway Protocol (BGP) networks are one type of L3VPN solution.An example of an IP-based Virtual Private Network is disclosed in U.S.Pat. No. 6,693,878. U.S. Pat. No. 6,665,273 describes a MPLS systemwithin a network device for traffic engineering.

One problem associated with existing IEEE 802.1 specifications is thatthe 12-bit VLAN ID can only support a combined total of up to 4,094broadcast domains and service instance domains. The 4K VLAN ID spacethus limits the number of VLANs or VPNs that can be handled, and isinadequate for operations over a SP MAN/WAN network. A proposed solutionto the scalability problem imposed by the 4K VLAN ID space limitation isdescribed in U.S. Patent Application Publication 2004/0165600.

Virtual Private LAN Service (VPLS) has recently emerged to meet the needto connect geographically dispersed locations with aprotocol-transparent, any-to-any connectivity service. VPLS is anarchitecture that delivers Layer 2 service that in all respects emulatesan Ethernet LAN across a WAN and inherits the scaling characteristics ofa LAN. All sites in a VPLS instance appear to be on the same LAN,regardless of location. In other words, with VPLS, customers cancommunicate as if they were connected via a private Ethernet LANsegment. Basically, VPLS offers a MPLS-based approach with multipointconnectivity for L2 services, i.e., multipoint Ethernet LAN services,often referred to as Transparent LAN Service (TLS). VPLS thus supportsthe connection of multiple sites in a single broadcast domain over amanaged IP/MPLS network. Since a VPLS is normally provided over aservice provider MAN/WAN network, it therefore needs to scale toaccommodate a very large number of VPNs (e.g., a large number ofcustomers, numerous services for each customer, and a large number ofcustomer sites).

Conceptually, VPLS can be thought of as an emulated Ethernet LAN networkwith each Virtual Switch Instance (VSI) being analogous to a virtualEthernet switch. Current VPLS models are described in the InternetEngineering Task Force (IETF) working group (WG) documentsdraft-ietf-l2vpn-vpls-ldp-03.txt and draft-ietf-l2vpn-vpls-bpg-02.txt,which are herein incorporated by reference. These documents address theaforementioned scalability problem in terms of the number of VPNs thatcan be supported. These VPLS models, however, create additional problemsin terms of Operations and Management (OAM) maintainability andscalability because of the very large number of pseudowire (PW) meshesrequired.

In the VPLS model described in the IETFdraft-ietf-l2vpn-vpls-ldp-03.txt, a VPLS instance has a filteringdatabase for supporting its own MAC address domain, and uses a set ofPWs per service instance for defining the broadcast domain of the L2VPN. It also uses split horizon mechanism on each set of PWs to preventloops in the MPLS/IP network. Since the current model uses a set of PWsper L2 VPN, the number of PWs that need to be supported per PE can bevery large, i.e., on the order of 100K or 1M (e.g., 10K L2 VPNs with10-100 sites per VPN). Considering existing requirements for partialmesh detection and timing constraints, it is extremely difficult to runa fast failure detection mechanism on a per PW basis for such a largenumber of PWs and exchange state information among PEs for partial meshdetection.

Thus, what is needed is a new VPLS architectural model that reduces thenumber of PWs in the network while maintaining scalability and supportfor a large number of VPNs as well as OAM.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood more fully from the detaileddescription that follows and from the accompanying drawings, whichhowever, should not be taken to limit the invention to the specificembodiments shown, but are for explanation and understanding only.

FIG. 1 is conceptual diagram that illustrates a PE device in accordancewith one embodiment of the present invention.

FIG. 2 shows one embodiment of the extended VLAN format utilized inaccordance with the present invention.

FIG. 3 is a diagram of a service provider network using the extendedVLAN mechanism to identify a VPLS instance according to one embodimentof the present invention.

FIG. 4 is a network diagram that illustrates a redundancy mechanismutilized in accordance with one embodiment of the present invention.

FIG. 5 is a partial network diagram that shows virtual trunk blocking inaccordance with one embodiment of the present invention.

DETAILED DESCRIPTION

A VPLS model that utilizes an extended VLAN (E-VLAN) mechanism thattremendously reduces the number of PWs in a VPLS system is described. Inthe following description specific details are set forth, such as devicetypes, protocols, configurations, etc., in order to provide a thoroughunderstanding of the present invention. However, persons having ordinaryskill in the networking arts will appreciate that these specific detailsmay not be needed to practice the present invention.

A computer network is a geographically distributed collection ofinterconnected subnetworks for transporting data between nodes, such asintermediate nodes and end nodes. A local area network (LAN) is anexample of such a subnetwork; a plurality of LANs may be furtherinterconnected by an intermediate network node, such as a router orswitch, to extend the effective “size” of the computer network andincrease the number of communicating nodes. Examples of the end nodesmay include servers and personal computers. The nodes typicallycommunicate by exchanging discrete frames or packets of data accordingto predefined protocols. In this context, a protocol consists of a setof rules defining how the nodes interact with each other.

Each node typically comprises a number of basic subsystems including aprocessor subsystem, a main memory and an input/output (I/O) subsystem.Data is transferred between main memory (“system memory”) and processorsubsystem over a memory bus, and between the processor and I/Osubsystems over a system bus. Examples of the system bus may include theconventional lightning data transport (or hyper transport) bus and theconventional peripheral component [computer] interconnect (PCI) bus.Each network node may also comprise other hardware units/modules coupledto system bus for performing additional functions. The processorsubsystem may comprise one or more processors and a controller devicethat incorporates a set of functions including a system memorycontroller, support for one or more system buses and direct memoryaccess (DMA) engines. In general, the single-chip device is designed forgeneral-purpose use and is not heavily optimized for networkingapplications.

In a typical networking application, packets are received from a framer,such as an Ethernet media access control (MAC) controller, of the I/Osubsystem attached to the system bus. A DMA engine in the MAC controlleris provided a list of addresses (e.g., in the form of a descriptor ringin a system memory) for buffers it may access in the system memory. Aseach packet is received at the MAC controller, the DMA engine obtainsownership of (“masters”) the system bus to access a next descriptor ringto obtain a next buffer address in the system memory at which it may,e.g., store (“write”) data contained in the packet. The DMA engine mayneed to issue many write operations over the system bus to transfer allof the packet data.

FIG. 1 is a conceptual block diagram of one embodiment of a PE device 10in accordance with the VPLS model of the present invention. PE device 10includes a processing engine (CPU) 11 coupled with a main memory 12. CPU11 processes packets received by a plurality of physical ports 13 facingtoward one or more CE devices. After processing, packets are deliveredto one or more output ports 15 that face toward the SP network core.Each port 15 includes one or more PWs 16.

In accordance with the present invention, each PW 16 functions as alogical link (e.g., an IEEE 802.1Q specification trunk) between bridgecomponents of two PE devices. This is a departure from the prior art useof PWs as part of VLAN emulation. That is, according to the traditionalVPLS model, a full mesh of PWs of a service instance emulates a providerVLAN with respect to the bridge component of a PE device. However, inaccordance with the present invention, the VLAN emulation model isdiscarded and each PW functions like a logical link transport mechanismthat carries the provider VLANs. According to the VPLS model of thepresent invention, each VPLS instance is identified by an extended VLAN(E-VLAN) tag that is generated by CPU 11 of PE device 10. Basically, CPU11 converts the incoming SP VLAN tag associated with packets arriving atports 13 into the E-VLAN tag format that is sent across the SP corenetwork.

FIG. 2 shows the E-VLAN tag format in accordance with one embodiment ofthe present invention. An Ethertype associated with the E-VLAN may beused to identify this extended tag in an Ethernet frame. A key featureof the E-VLAN tag format is a 20-bit VLAN ID/Service ID field thatallows identification, in certain applications, of up to one milliondifferent service instances. Also included is a 4-bit Class of Service(CoS) field, a Discard eligible (D) bit, a FCS (F) bit, a customer MACaddress encapsulation (M) bit, and a stack (S) bit that indicates thatVLAN stacking is utilized in the data packet format. Setting of the Mbit indicates the entire customer frame, including the customer's MACaddress, is encapsulated in the Ethernet frame. In cases where the M bitis set, the provider MAC address is used for tunneling through the SPnetwork. These latter two features will be discussed in more detailbelow.

In one implementation, the E-VLAN tag of FIG. 2 is utilized as a VPLSservice instance identifier (i.e., customer VPN ID), with the E-VLAN tagbeing embedded within the Ethernet frame. In this manner, up to onemillion service instances may be supported in transmission across the SPcore network.

FIG. 3 is a simplified example of a SP network in accordance with oneembodiment of the present invention in which a core network 20 is shownconnected to a pair of Ethernet access networks 21 & 22 via networkprovider edge (n-PE) devices 32 & 33, respectively. User-facing provideredge (u-PE) devices 31 & 34 connect respective customer edge (CE)devices 41 & 42 to Ethernet access networks 21 & 22. In thisillustration, n-PE devices 32 and 33 are implemented in accordance withthe PE device model shown in FIG. 1. That is, for traffic passing fromleft to right in FIG. 3, n-PE device 32 maps the 12-bit provider VLAN IDassociated with customer edge device 41 into a 20-bit E-VLAN tagidentifier that is then sent over core network 20. At the other end,n-PE device 33 translates the 20-bit E-VLAN tag back to a standard12-bit provider VLAN ID, which eventually passes to CE device 42 at thedestination end.

It is appreciated that each of the u-PE and n-PE devices shown in theembodiment of FIG. 4 are configured to both convert 12-bit VLAN IDs intoE-VLAN identifiers in the direction across core network 20, and toconvert E-VLAN identifiers into 12-bit VLAN IDs in the direction fromcore network 20 to the CE device. In other words, the PE devices 32 & 33at the edge of the core and access networks are capable of handling bothingress and egress traffic in the manner described above. By way ofexample, processing of the identifiers may be performed by a softwareroutine running on CPU 11 of the corresponding PE device.

Note that in accordance with the present invention, the filteringdatabase normally associated with each customer is unchanged; that is,the filtering database is used as before (prior model) for eachcustomer. But instead of using a full mesh of PWs to designate abroadcast domain over the core network (i.e., to emulate a providerVLAN), the E-VLAN mechanism described above is utilized. To limit thebroadcast domain associated with a provider VLAN (or VPLS instance) overa set of PWs, a modified version of GARP (Generic Attribute RegistrationProtocol) VLAN Registration Protocol (GVRP) is run, which modifiedversion is herein referred to as Extended GVRP (E-GVRP), among the PEdevices (or n-PE devices only). GVRP is a known application defined inthe IEEE 802.1Q standard that allows for the control of 802.1Q VLANs,i.e., 802.1Q-compliant VLAN pruning and dynamic VLAN creation on 802.1Qtrunk ports. GVRP basically allows a switch to exchange VLANconfiguration information with other GVRP switches, prune unwanted VLANsand their associated broadcast, multicast, and unicast traffic, anddynamically create and manage VLANs on switches connected through 802.1Qtrunk ports.

The E-GVRP is essentially a compact GVRP that has a coding used tocompress the VLAN information for up to 4K VLANs into a single Ethernetframe. In the E-GVRP, a jumbo Ethernet frame is utilized to carry theinformation needed for a large number of E-VLANs. Like GVRP, E-GVRP onlyruns among PE devices (or n-PEs); it does not interfere with and runsindependently from each access domain's GVRP. Using E-GVRP each PEdevice may indicate to other PE devices what VPLS instances (E-VLANs) itis interested in on a given PW. Thus, the other PE devices may operateby only sending traffic from those VLANs over that PW, thereby limitingthe scope of broadcast domain for each E-VLAN.

It should be understood that the Multiple VLAN Registration Protocol(MVRP) may also be utilized in conjunction with the present invention inreplacement for GVRP for the purposes of auto-discovery and notificationof active VLANs.

FIG. 4 is a network diagram that illustrates how redundancy is handledin accordance with one embodiment of the present invention. FIG. 4 showsaccess domains (i.e., islands) 50 and 70 on opposite sides of corenetwork 20. In FIG. 4, n-PE devices 60 & 61 connect with nodes 51-55 ofisland 50, and n-PE devices 80 & 81 connect with nodes 71-77 of island70. A full mesh of PWs 91-94 connects n-PE devices 60 & 61 with n-PEdevices 80 & 81.

Each of islands 50 and 70 runs its own Spanning Tree Protocol (STP), orsome variant of STP, e.g., MSTP or RSTP. As is well known, switches in anetwork running STP gather information about other switches in thenetwork through an exchange of control messages called Bridge ProtocolData Units (BPDUs). BPDUs contain information about the transmittingswitch and its ports, including its switch and port Media Access Control(MAC) addresses and priorities. The exchange of BPDU messages results inthe election of a root bridge on the network, and computation of thebest path from each switch to the root switch. To provide pathredundancy, STP defines a tree from the root that spans all of theswitches in the network, with certain redundant paths being forced intoa standby (i.e., blocked) state. If a particular network segment becomesunreachable the STP algorithm reconfigures the tree topology andre-establishes the link by activating an appropriate standby path.

According to one embodiment, link and node level redundancy is achievedby BPDU loopback at the remote n-PE device. In the example shown in FIG.4, a BPDU packet sent by n-PE devices 60 or 61 across any of PWs 91-94is looped back via another PW. This loopback operation is indicated bythe dashed lines in FIG. 4 shown connecting PW 91 & 93 and PW 92 & 94.By looping the BPDU back, it looks to the island (e.g., island 50)sending the BPDU as if the two PWs are actually connected together(i.e., like a LAN segment). This means that the local STP in island 50running over n-PE devices 60 & 61 can block the appropriate virtualtrunk, thus providing redundancy. This blocking function is illustratedin FIG. 5 by the shaded blocks at n-PE device 61 for each of the two PWpaths from n-PE device 60 to n-PE device 61 (looped back at the remoten-PE devices 80 & 81). For instance, one path from n-PE device 60 ton-PE device 61 includes PWs 91 & 93, while the other path includes PWs94 & 92.

Practitioners will appreciate that the examples of FIGS. 4 & 5illustrate how the provider BPDU path is exactly the same as that of theprovider data.

In addition, since PWs function as a transport mechanism for VPLSidentifiers in the present invention, either full or partial meshes maybe implemented among the n-PE devices so connected across the corenetwork. In other words, problems caused by partial meshes in the priorart VPLS model are obviated in the present invention since PWs are nolonger part of an emulated VLAN. Instead, PWs are used as logical links,which means that bridge protocols may be leveraged to take care of PWfailures. The present invention also allows for an efficient recoverymechanism since a single PW failure does not result in a PE failure (aswas often the case in the prior art). Furthermore, Ethernet OAM protocol(IEEE 802.1ag) can be readily applied to the VPLS model of the presentinvention.

It should be understood that elements of the present invention may alsobe provided as a computer program product which may include amachine-readable medium having stored thereon instructions which may beused to program a computer (e.g., a processor or other electronicdevice) to perform a sequence of operations. Alternatively, theoperations may be performed by a combination of hardware and software.The machine-readable medium may include, but is not limited to, floppydiskettes, optical disks, CD-ROMs, and magneto-optical disks, ROMs,RAMs, EPROMs, EEPROMs, magnet or optical cards, propagation media orother type of media/machine-readable medium suitable for storingelectronic instructions. For example, elements of the present inventionmay be downloaded as a computer program product, wherein the program maybe transferred from a remote computer (e.g., a server) to a requestingcomputer (e.g., a customer or client) by way of data signals embodied ina carrier wave or other propagation medium via a communication link(e.g., a modem or network connection).

Additionally, although the present invention has been described inconjunction with specific embodiments, numerous modifications andalterations are well within the scope of the present invention.Accordingly, the specification and drawings are to be regarded in anillustrative rather than a restrictive sense.

1. A processor-implemented method of operation for a network-facingprovider edge device (n-PE) of a core network, the method comprising:receiving a packet from an access network, the packet having a firstVirtual Local Area Network (VLAN) tag of a first predetermined bitlength; mapping the service instance identifier of the first VLAN taginto a second VLAN tag of a second predetermined length greater than thefirst predetermined bit length, the second VLAN tag identifying aVirtual Private LAN service (VPLS) instance; sending the packet with thesecond VLAN tag across a service provider (SP) core network via apseudowire (PW) that functions as a logical link that carries a providerVLAN to another PE device; and executing an application that exchangesVLAN configuration information with other network devices; whereinmapping the service instance identifier includes generating the secondVLAN tag based on the exchanged VLAN configuration information.
 2. Theprocessor-implemented method of claim 1 wherein the applicationcomprises a version of GARP (Generic Attribute Registration Protocol)VLAN Registration Protocol (GVRP).
 3. The processor-implemented methodof claim 1 wherein core network comprises a Multi-protocol labelswitching (MPLS)/Internet Protocol (IP) network.
 4. Aprocessor-implemented method of operation for a network-facing provideredge (n-PE) of a core network, the method comprising: receiving a packetfrom an access network, the packet being in a first format and includinga first Virtual Local Area Network (VLAN) tag of a first predeterminedbit length; converting the packet from the first format into a secondformat in which the first VLAN tag is mapped into a second VLAN taghaving a second predetermined bit length format, the secondpredetermined bit length being greater than the first predetermined bitlength; the second VLAN tag identifying a Virtual Private LAN Service(VPLS) instance and being embedded within an Ethernet frame; and sendingthe packet with the second VLAN tag across a service provider (SP) corenetwork via a pseudowire (PW) that functions as a logical link thatcarries a provider VLAN to another PE device executing an applicationthat exchanges VLAN configuration information with other networkdevices; wherein mapping the service instance identifier includesgenerating the second VLAN tag based on the exchanged VLAN configurationinformation.
 5. The processor-implemented method of claim 4 wherein thelogical link comprises an IEEE 802.1Q-compatible trunk.
 6. Theprocessor-implemented method of claim 4 wherein the access networkcomprises an Ethernet access network.
 7. The processor-implementedmethod of claim 4 wherein the application comprises a version of GARP(Generic Attribute Registration Protocol) VLAN Registration Protocol(GVRP).
 8. A network-facing provider edge (n-PE) device comprising: aport to receive a packet from an access network, the customer framehaving a first Virtual Local Area Network (VLAN) tag of a firstpredetermined bit length, the first VLAN tag including a serviceinstance identifier; and a processing unit that converts the packet fromthe first format into a second format in which the service instanceidentifier of the first VLAN tag is mapped into a second VLAN tag havinga second predetermined bit length format, the second predetermined bitlength being greater than the first predetermined bit length, theprocessing unit being operable to send the packet in the second formatacross a service provider (SP) core network via a pseudowire (PW) thatfunctions as a logical link that carries a provider VLAN to a secondn-PE device; wherein the processing unit is further operable to executean application that exchanges VLAN configuration information with thesecond n-PE device, and wherein the processing unit is further operableto generate the second VLAN tag based on the exchanged VLANconfiguration information.
 9. The n-PE device of claim 8 wherein thelogical link comprises an IEEE 802.1Q-compatible trunk.
 10. The n-PEdevice of claim 8 wherein the application comprises a version of GARP(Generic Attribute Registration Protocol) VLAN Registration Protocol(GVRP).
 11. A provider edge device comprising: a plurality of ports; andmeans for receiving a packet received at one of the ports in a firstformat, the first format including a first Virtual Local Area Network(VLAN) tag of a first predetermined bit length, the first VLAN tagincluding a service instance identifier, and for converting the packetinto a second format in which the service instance identifier of thefirst VLAN tag is mapped into a second VLAN tag having a secondpredetermined bit length format, the second predetermined bit lengthbeing greater than the first predetermined bit length, the means alsofor embedding the second VLAN tag in an Ethernet frame and seconding theframe across a service provider (SP) core network via a pseudowire (PW)that functions as an IEEE 802.1Q-compatible trunk link that carries aprovider VLAN to a second n-PE device; wherein the means for convertingthe packet into a second format is further operable to execute anapplication that exchanges VLAN configuration information with thesecond n-PE device, and wherein the means for converting the packet intoa second format is further operable to generate the second VLAN tagbased on the exchanged VLAN configuration information.
 12. A serviceprovider (SP) network, comprising: a core network that includes aplurality of network-facing provider edge (n-PE) devices connected by aset of pseudowires (PWs), each of the PWs functioning as a logical linkthat carries a provider VLAN between a pair of n-PE devices; a firstEthernet access network configured to transmit a packet of a firstformat that includes a first Virtual Local Area Network (VLAN) taghaving a 12-bit length to a first n-PE device of the core network, thefirst n-PE device being operable to convert the packet into a secondformat in which the first VLAN tag is mapped to a second VLAN tag of a20-bit length that identifies a Virtual Private LAN Service (VPLS)instance, the first n-PE device being further operable to embed thesecond VLAN tag in an Ethernet frame and send the frame across the corenetwork to a second n-PE device via a first PW, the second n-PE devicebeing operable to convert the packet back to the first format; and asecond Ethernet access network configured to deliver the packet receivedin the first format from the second n-PE device to a user-facingprovider edge (u-PE) device that connects with a customer site; whereineach of the first and second n-PE devices is further operable to executean application that exchanges VLAN configuration information, andwherein the first n-PE device is further operable to generate the secondVLAN tag based on the exchanged VLAN configuration information.
 13. TheSP network of claim 12 wherein the application comprises a version ofGARP (Generic Attribute Registration Protocol) VLAN RegistrationProtocol (GVRP).
 14. The SP network of claim 12 wherein the core networkfurther includes third and fourth n-PE devices connected with the firstand second Ethernet access networks, respectively.
 15. The SP network ofclaim 14 wherein the mesh is a full mesh, wherein a second PW connectsthe third and fourth n-PE devices, a third PW connects the first andfourth n-PE devices, and a fourth PW connects the third and second andthird n-PE devices.
 16. The SP network of claim 15 wherein each of thefirst and third n-PE devices, and the second and fourth n-PE devices,respectively associated with the first and second Ethernet accessnetworks, are operable to run a local Spanning Tree Protocol (STP). 17.The SP network of claim 15 wherein the second n-PE device is operable toloop back a Bridge Protocol Data Unit (BDPU) packet received from thefirst n-PE device via the first PW to the third n-PE device via thefourth PW.